SAN DIEGO -- Workers at an Otay Mesa warehouse discovered almost eight tons of marijuana with an estimated street value of $4.5 million while unloading furniture off a tractor-trailer from Mexico, officials said Thursday.

Federal agents Wednesday seized 15,433 pounds of marijuana, which was wrapped in pharmaceutical boxes, Home Depot boxes and heavy duty trash bags, said Lauren Mack, spokeswoman for U.S. Immigration and Customs Enforcement.

A 32-year-old truck driver crossed the border without a problem and delivered the load to a warehouse around 3 p.m. Tuesday, Mack said.

Workers unloading furniture from the truck found the marijuana a short time later and reported it to federal agents, Mack said.

Agents questioned the driver but found no reason to arrest him, Mack said.

The truck is used by three Mexican companies, and agents investigated how the truck managed to slip past border inspectors, Mack said.